provium.toml

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provium.toml is the only config file Provium reads. The default location is ./provium.toml; override with --config <path>.

The schema has two top-level keys: [provium] for runner settings, and [profiles.<name>] for per-VM-type tuples. Both are optional individually — an empty provium.toml parses cleanly but won't be useful for anything (no profiles means provium:vm(name, profile) won't find any profile to look up).

Minimum useful config #

[provium]
roots = ["tests"]

[profiles.peios]
kernel  = "/path/to/bzImage"
initrd  = "/path/to/initrd.cpio.gz"
cmdline = "console=ttyS0 quiet"

This declares one test root and one profile. provium tests/ will scan tests/ for *.test.lua, and tests can call provium:vm("name", "peios").

[provium] section #

roots #

[provium]
roots = ["tests", "vendor/upstream-tests"]

When roots is empty (or unset), provium <paths> scans whichever paths you pass on the CLI; if you also omit those, it scans the current directory.

For most projects, set roots = ["tests"] (or whichever directory contains your tests) so that:

• provium (no arg) walks the test tree.
• provium fixture build foo finds tests/foo.fixture.lua.
• Tests can require("helpers.assert_pingable") and Provium resolves it as tests/helpers/assert_pingable.lua.

cache_dir #

[provium]
cache_dir = "/var/cache/provium/fixtures"

Useful for:

• Per-machine caches on shared hosts (default is per-user, set to a system-wide path for shared CI runners).
• Fast scratch storage (point at an SSD or tmpfs for build performance).
• Large dedicated cache (point at a partition with more headroom than ~/.cache).

The directory is created on first build. If the path is unreadable / unwritable at startup, eviction silently skips and the next build attempt errors with the underlying I/O error.

cache_max_size #

[provium]
cache_max_size = "100G"

When the cache exceeds the cap, Provium sorts entries by access time and deletes oldest until total size is under the cap. Each successful restore bumps the entry's atime so popular fixtures stay hot.

[profiles.<name>] blocks #

Each [profiles.<name>] block declares one (kernel, initrd, cmdline, guest_os) tuple. Test code looks them up by name: provium:vm("v", "<name>").

You can have any number of profiles; tests pick whichever they need.

kernel #

[profiles.peios]
kernel = "/build/peios/bzImage"

Path validation (does the file actually exist?) happens at VM-boot time, not config-load time. This lets a single provium.toml be portable across machines that have different kernel layouts.

May be omitted when root names a composed Peios root, in which case the kernel is found inside it.

root #

[profiles.kernel-only]
root = "{out}/root"

Set this instead of kernel when the profile's build composes a root, so the profile does not also have to know where in that root a kernel lands. A kernel version bump then moves nothing in the config. kernel, when set, wins.

Resolution happens at VM-boot time, after the build has run — which is the only order that works, since the build is what produces the root. Two kernels in one root is an error rather than a choice made quietly: set kernel to say which.

initrd #

[profiles.peios]
initrd = "/build/peios/initrd.cpio.gz"

By default, Provium injects the provium-agent binary at /sbin/provium-agent by concatenating a small overlay cpio onto your initrd at launch (the kernel unpacks concatenated gzip cpios into a single rootfs). The agent boots as PID 1 and forks immediately: the child becomes the vsock listener, the parent execs your initrd's /init, which therefore takes over PID 1. In this chained layout the agent deliberately mounts nothing first — your init owns the mount and pivot sequence exactly as it would alone. (Only on an agent-only initrd, with no user /init, does the agent perform the pseudo-FS mounts itself.) Userspace runs as it would have on its own; the agent runs alongside as PID 2.

Three consequences:

• Your initrd doesn't need to know about Provium. A vanilla distro initramfs, a buildroot image, or a from-scratch cpio with just /init will all work.
• Your /init runs as PID 1. If your tests need PID-1 init duties (signals, child reaping), they happen in your init as before.
• The merged initrd is content-hash cached under <scratch_root>/agent-overlay-cache/<sha256>.cpio.gz. Subsequent boots of the same (initrd, overlay) pair pay nothing.

To opt out (e.g. when your initrd already bundles an agent at the path Provium would set), set inject_agent = false on the profile.

No initrd at all #

Omitting initrd means the VM has no userspace of its own: the agent overlay is the whole initramfs. Nothing is concatenated and nothing is cached — the overlay file is handed to QEMU as it stands. It carries the agent but no /init, so the agent comes up as PID 1 in its standalone mode and performs the pseudo-FS mounts itself.

That is the shape a kernel conformance suite wants, where the point is that nothing but the kernel is reachable from a test. It also saves such a project vendoring an initrd cpio it would never otherwise need.

inject_agent = false with no initrd is rejected: without injection there is no overlay to stand in for the missing file, and so nothing to boot.

disks #

[profiles.peios]
disks = [
  { path = "{out}/peios.iso", id = "medium", readonly = true },
]

Per disk:

Put a disk here when the image is part of the system under test rather than part of a test. A boot medium an initramfs scans for is a sibling of initrd and root: every test boots the same one, and the profile's build already owns keeping it fresh. Put it in vm:boot({disks = …}) when it varies per test — a blank disk to install onto, a deliberately damaged filesystem.

A disk cannot come from vm:attach_disk, which runs after boot. Anything the guest's firmware or initramfs does with a block device happens long before there is an agent to call that, so a medium the boot itself depends on has to be on the bus at the guest's first instruction.

Ids are one namespace across the profile's disks and the boot's, because they end up on one QEMU command line. A duplicate within the profile is rejected when the config loads; a boot disk reusing a profile id fails the launch with disk id \` is already attached by the profile`. Profile disks are always attached first, so the medium a profile boots from keeps its device name no matter what a test adds.

Mediated disks #

A disk with mediated = true still reaches the guest as an ordinary virtio-blk device. What changes is who is underneath it: Provium serves the image over an NBD server of its own and holds each write until the guest flushes it, so disk:power_cut() drops precisely the writes that were never made durable.

Killing the VM is not a substitute for that. Unflushed data written through an ordinary drive sits in the host's page cache, which outlives the process — so a test that killed QEMU would find everything intact and report durability it had never demonstrated.

The drive is attached cache=none as a consequence rather than as a tuning choice: a read QEMU could satisfy from its own cache is a read Provium never sees.

Mediation is opt-in per disk. power_cut on a disk without it fails naming the disk, rather than quietly doing nothing.

inject_agent #

[profiles.peios]
inject_agent = false

If your cmdline already pins a different rdinit=PATH, the launch errors with a clear conflict message rather than silently overriding. Either remove the conflicting rdinit=, or set inject_agent = false.

agent_overlay_path #

[profiles.peios]
agent_overlay_path = "/usr/local/share/provium/agent-overlay.cpio.gz"

When unset, Provium tries (in order): the PROVIUM_OVERLAY env var, then <provium-binary-dir>/../share/provium/agent-overlay.cpio.gz, then walks up the binary's directory tree looking for dist/agent-overlay.cpio.gz (covers in-development runs from target/). Set this field — or the env var — when none of those apply.

agent_boot_timeout #

[profiles.peios]
agent_boot_timeout = 8.0

Thirty seconds is a generous ceiling for a guest that is going to come up, and a long time to wait for one that is not. Lower it on a profile whose guest boots quickly and whose tests deliberately boot configurations that cannot reach an agent — an init that halts, an image with no init at all — because for those the timeout is not a safety margin but the length of every passing test. vm:boot's agent_timeout overrides it for a single boot.

Raise it instead for a guest that legitimately takes longer than thirty seconds: a large image, a slow filesystem check, a host under heavy parallel load.

cmdline #

[profiles.peios]
cmdline = "console=ttyS0 quiet"

vm:boot({kernel_cmdline = "..."}) overrides the whole command line for one boot; vm:boot({kernel_cmdline_append = "..."}) keeps it and adds tokens after it.

Provium always appends console=ttyS0 if absent. The kernel happily uses multiple console= directives, so any user-set values are preserved alongside. The reason: the QEMU command wires the serial port into Provium's console capture, so the kernel's printk needs to land there for failure diagnostics to be visible. Without console=ttyS0, PID 1's /dev/console may resolve to a device QEMU doesn't capture, and writes to stderr can fail and crash userspace.

Common additions:

• loglevel=7 — verbose kernel logging for debugging.
• nokaslr — for reproducible kernel addresses in panic dumps.
• panic=1 — panic immediately rather than hanging on unrecoverable errors.

cmdline_file #

[profiles.peios]
cmdline_file = "../dist/peios-experimental-2026.8/root/usr/share/live-boot/cmdline"
cmdline      = "loglevel=7"   # optional; appended after the file

All whitespace in the file — including newlines — is collapsed to single spaces, then the inline cmdline (if any) is appended after. Because the kernel applies last-wins semantics to most repeated parameters (init=, loglevel=, …), an inline token overrides the file's value for those.

The point is to stop the command line from drifting. If a builder bakes init=/usr/bin/protoinit into the image's cmdline and you hand-copy that into cmdline, the two silently diverge the next time the builder changes. Pointing cmdline_file at the builder's output means Provium reads the authoritative value every boot. See Dynamic profiles.

guest_os #

[profiles.peios]
guest_os = "peios"

Validated at config load time. A profile with guest_os = "linux" (or any other value) errors with profile \` has guest_os = `linux`, only `peios` is supported in v1`.

The field exists to future-proof the schema for other ports — when there's a Windows agent, this would be how a profile selects it.

build #

[profiles.peios]
build        = "peiso iso specs/peios.toml --out {out}"
kernel       = "{out}/root/usr/lib/modules/<release>/vmlinuz-<release>"
initrd       = "{out}/root/system/boot/initramfs.cpio.zst"
cmdline_file = "{out}/root/usr/share/live-boot/cmdline"

The literal token {out} — in build and in the path fields — expands to this profile's build-output directory (see build_out), so the command's --out and the kernel/initrd/cmdline_file Provium later reads are the same path and cannot drift.

Provium tracks no staleness: the command runs every invocation. Making rebuilds cheap when nothing changed is the builder's job, not Provium's. Skip the hook with --no-build, or run it without booting via provium prepare. Full treatment on Dynamic profiles.

build_out #

[profiles.peios]
build_out = "/tmp/provium-builds/peios"

When unset, the default base is resolved like the fixture cache — $PROVIUM_BUILD_DIR, then $XDG_CACHE_HOME/provium/builds, then ~/.cache/provium/builds, then /tmp/provium-builds — with the profile name appended. Provium creates the directory before running build but never wipes it: the build command owns its contents (so it can keep its own incremental-build caches there).

Multiple profiles #

You can declare any number of [profiles.<name>] blocks; tests pick one by name per VM. Patterns for multi-profile setups (debug builds, cross-version testing, feature-flag gating) are on Profiles.

from_dir #

[profiles]
from_dir = "profiles"

Reads profiles from a directory instead of writing them inline. Each subdirectory holding a profile.provium.toml is one profile, named after the directory:

provium.toml
profiles/
  kernel-only/
    profile.provium.toml
  full-system/
    profile.provium.toml

gives the profiles kernel-only and full-system. A subdirectory without that file is not a profile and is skipped rather than rejected, so a profile directory may keep whatever else it needs beside its config. A from_dir that names a directory holding no profile at all is an error.

The file's contents are the fields above — everything from [profiles.<name>] except the name, which the directory supplies.

Adding a testset becomes mkdir, with nothing central to keep in sync. That matters most for a repository whose whole purpose is holding many of them.

from_dir and inline blocks may both appear. A discovered profile whose name collides with an inline one is an error, not a silent winner.

What a discovered profile's paths are relative to #

Its own directory — both the paths it names and the directory its build runs in. An inline profile keeps resolving against Provium's current directory, as it always has.

This is the rule that makes a profile directory self-contained: it can be moved, copied or renamed and still mean what it says. It also means the same relative path means the same thing whether it is written in the shared config or in a profile beside it, which is not true if everything resolves against one directory.

{out} paths are exempt, since a build-output directory is absolute and has nothing to do with where the profile lives.

# profiles/kernel-only/profile.provium.toml
#
# Both specs are named relative to this directory, and the command runs
# here, so `../../peiso.toml` is the repository's.
# `--out` must not already exist, and Provium never wipes {out} —
# clearing it is the build's own job.
build   = "rm -rf {out}/root && peiso root ../../peiso.toml peiso.toml --out {out}/root"
root    = "{out}/root"
cmdline = "console=hvc0 quiet panic=1"

Important: the fixture cache key folds in EVERY profile's kernel + initrd identifier. Adding a new profile invalidates the entire fixture cache. This is intentional: a new kernel could behave differently, so existing fixtures are no longer trustworthy. See Profiles — What happens to the cache when profiles change.

Configuration loading #

Errors:

All three abort the run with exit code 2.

Worked example #

[provium]
roots          = ["tests", "internal-tests"]
cache_dir      = "/srv/provium-cache"
cache_max_size = "200G"

[profiles.peios]
kernel   = "/srv/peios-builds/latest/bzImage"
initrd   = "/srv/peios-builds/latest/initrd.cpio.gz"
cmdline  = "console=ttyS0 quiet panic=1"
guest_os = "peios"

[profiles.peios-mainline]
kernel   = "/srv/peios-builds/mainline/bzImage"
initrd   = "/srv/peios-builds/mainline/initrd.cpio.gz"
cmdline  = "console=ttyS0 quiet panic=1"
guest_os = "peios"

[profiles.peios-debug]
kernel   = "/srv/peios-builds/debug/bzImage"
initrd   = "/srv/peios-builds/debug/initrd.cpio.gz"
cmdline  = "console=ttyS0 debug loglevel=7 nokaslr panic=1"
guest_os = "peios"

This declares three profiles (production, mainline, debug), centralises the cache on a 200 GiB dedicated mount, and scans both tests/ and internal-tests/.

See also #

• Project structure — the broader project layout.
• VM reference — boot_opts.kernel_cmdline overrides and kernel_cmdline_append.
• Profiles — patterns for using multiple profiles.

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